Fix: Restore Native caching business logic and implement 3-mode launcher

- Implemented Default, Onsite, and Native launcher modes in launcher_file_cont.svelte.
- Restored background pre-caching logic with configurable timers in new LauncherBackgroundSync component.
- Fixed standard browser download regression for regular website mode.
- Modernized electron_relay to TypeScript and standardized bridge detection in layout.
- Detailed startup and background sync technical flow in documentation.

src/routes/journals/ae_comp__modal_journal_export.svelte

@@ -131,10 +131,10 @@
 
         <!-- Preview Area -->
         <div class="form-control">
-            <label class="label flex justify-between items-center">
+            <div class="label flex justify-between items-center">
                 <span class="label-text">Preview</span>
                 <span class="text-[10px] opacity-50 uppercase tracking-widest">{selected_template.name}</span>
-            </label>
+            </div>
             <textarea 
                 class="textarea h-64 font-mono text-xs bg-gray-50 dark:bg-gray-900"
                 readonly